The present invention relates to techniques for enhancing the speed of graphics processing performed on workstations, personal computers and the like. More particularly, the invention relates to a graphics system for utilizing a plurality of rendering devices.
In a graphics system implemented by a workstation or the like, graphics processing is accelerated conventionally by a setup comprising a plurality of geometric processors for performing geometric computations in graphics, as well as a plurality of rendering processors for generating pixels. For example, a Z-merger image composition scheme involving a plurality of rendering devices to generate three-dimensional images parallel is used to increase the processing speed of "Subaru: A High-Speed High-Performance 3D CG System" which was discussed in the autumn 1992 symposium of the Institute of Electronics, Information and Communication Engineers (proceedings, pp. 6-602-207). The disclosed system utilizes a plurality of rendering devices, each made up of a geometric processor, a rendering processor and a frame memory. On the level of pixels in which each rendering device effects its output, the system compares depth data (Z values) per pixel so that the color of each foreground pixel is selected. A final image is obtained by the system merging outputs from a plurality of rendering devices.
One advantage of the conventional technique mentioned above is that it is easy to shorten the time for image generation by simply adding more rendering devices, as discussed illustratively by Foley, van Dam, Feiner and Hughes in "Computer Graphics: Principle and Practice" (from Addison Wesley, pp. 906-907).
It should be noted that the disclosed system mentioned above with its Z-merger scheme simply selects pixels during Z value comparison and does not generate new pixel data. This means that the system has difficulty evaluating in Z values any transparent object which lets light pass therethrough. In some cases, transparent objects are not adequately displayed.